1. Field of the Invention
The present invention relates to an autoinjector syringe for administering a beneficial agent to a patient. Particularly, the present invention is directed to a syringe including a spring-activated plunger and a spring deployed extendable shroud in combination with a needle or similar penetrator.
2. Description of Related Art
The use of a sharp-pointed piercing element, such as a syringe needle or the like, entails the risk of accidental needle sticks. To avoid such accidents, a variety of safety systems are known and available to protect the user of a syringe.
A first type of safety system includes a rigid cylindrical safety shield arranged to telescope over the syringe barrel. Such a shield can be moved between a retracted position to expose the syringe needle for use, and an extended position to surround the needle with the shield. For example, U.S. Pat. No. 6,419,658, U.S. Pat. No. 6,322,540, U.S. Pat. No. 6,319,234, U.S. Pat. No. 6,319,233, U.S. Pat. No. 4,425,120, U.S. Pat. No. 4,573,976, U.S. Pat. No. 4,850,994 and U.S. Pat. No. 4,923,447 disclose various extendable shield systems for a hypodermic syringe. It is ordinarily desirable to lock the needle shields in the protected position, and a number of prior art designs provide for such locked conditions. Furthermore, some systems, such as those disclosed in U.S. Pat. No. 5,201,708, U.S. Pat. No. 5,242,240 and U.S. Pat. No. 5,318,538 are also designed to allow the shields to be retracted from their locked, extended positions.
The above-described device using a spring loaded sheath can be disadvantageous because the spring and shroud are generally mounted on the outside of the syringe barrel and are thereby vulnerable to mechanical interference with foreign objects. Moreover, such devices are manually deployed, which is not particularly conducive for self-administering medication by those who suffer from arthritis or similar ailments that limit digital dexterity.
Another type of safety system has been developed for use with a device commonly referred to as an autoinjector. An autoinjector is generally a syringe configured to automatically extend a needle and inject a beneficial agent into a patient when a button or similar actuator is deployed. Hence, it is known for some autoinjectors to be configured to retract the needle into the housing of the device when the injection is complete. Devices of this type are described, for example, in U.S. Pat. No. 6,099,503, U.S. Pat. No. 5,779,677, and U.S. Pat. No. 5,300,030. These types of devices are advantageous because only a single hand is needed to complete an injection. Furthermore, the needle can be configured to be extendable such that the syringe needle is not normally visible to the user before or after the injection. This is advantageous for self-administered drug therapy.
Such conventional methods and systems generally have been considered satisfactory for their intended purpose. However, the autoinjector described above can not be used for its intended purpose if the mechanism that returns the needle into the housing should fail for some reason. Stated another way, if the needle does not retract automatically, the user has no safe means of covering the needle point.
There thus remains a continued need for an efficient and economic method and system for automatically injecting a beneficial agent that is easy to use and helps prevent against accidental needle sticks after use.
The purpose and advantages of the present invention will be set forth in and apparent from the description that follows, as well as will be learned by practice of the invention. Additional advantages of the invention will be realized and attained by the methods and systems particularly pointed out in the written description and claims hereof, as well as from the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the invention is directed to a syringe including a housing having a proximal end and a distal end. The housing has a reservoir disposed therein. The syringe also includes a plunger to be received by the reservoir. The plunger is moveable between a first plunger position and a second plunger position. A plunger spring is also provided to urge the plunger toward the second plunger position when the plunger spring is deployed. The plunger spring can be deployed by an actuator. The syringe also includes a needle or similar penetrator proximate the distal end of the housing. Also provided is a shroud coupled with the housing. The shroud is moveable between a retracted position and an extended position. The shroud surrounds at least a portion of the needle when in the extended position. A shroud spring is biased to urge the shroud toward the extended position when the shroud spring is deployed. Further, an interlocking assembly in communication with the shroud is provided. The interlocking assembly has a first condition to maintain the shroud in the retracted position and a second condition to deploy the shroud spring and allow movement of the shroud toward the extended position.
Preferably, the interlocking assembly can be coupled with the plunger so as to be switched from the first condition to the second condition when the plunger is moved to the second plunger position. For example, the interlocking assembly can include at least one flexible tab provided on the shroud and an engagement surface provided on the plunger, whereby the engagement surface flexes the tab when the plunger is moved to the second plunger position. Alternatively, the interlocking assembly can include a switch operable from outside the housing to manually switch the interlocking assembly from the first condition to the second condition.
In accordance with a further aspect of the invention, the actuator can include an engagement element to retain the plunger in the first position. The engagement element acts to release the plunger and thus deploy the plunger spring when the actuator is actuated. In a preferred embodiment, the plunger spring can be a mechanical spring element although known springs, such as hydraulic or pneumatic, can be used. The syringe can further comprise a removable cover positioned on the distal end of the housing before the syringe is used.
Optionally, the needle is caused to be in fluid communication with the reservoir when the plunger is moved toward the second plunger position.
Additionally, the needle can be displaceable from a first needle position to a second needle position, such that the point of the needle extends from the housing when in the second needle position. The needle thus can be moved to the second needle position when the plunger is moved from the first plunger position toward the second plunger position.
Alternatively, and in accordance with a further aspect of the invention, the needle can be secured to the reservoir and the reservoir can be displaced with the needle.
In accordance with a further aspect of the invention, the syringe is provided with at least one guide element to provide registration between the reservoir and the plunger. The at least one guide element has a proximal end and a distal end. In one embodiment of the invention, the distal end of the guide element is fixedly attached to a mounting element that surrounds the reservoir. The mounting element is attached at a desired location along the reservoir, such as the proximal end of the reservoir. The mounting element may also be attached at the distal end of the reservoir.
Additionally, a locking assembly configured to inhibit movement of the shroud when moved to the extended position can also be provided. The locking assembly can include a protuberance to be received by a corresponding recess.
The invention also includes a method that includes providing a syringe as described above; loading a beneficial agent in the reservoir of the syringe; positioning the needle of the syringe at an injection site of a patient; moving the plunger toward the second plunger position to dispense the beneficial agent from the reservoir through the needle; and switching the interlocking assembly to the second condition to deploy the shroud spring and allow movement of the shroud toward the extended position. Optionally, the movement of the shroud toward the extended position provides an indication to a patient that beneficial agent has been injected.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide further explanation of the invention claimed.
The accompanying drawings, which are incorporated in and constitute part of this specification, are included to illustrate and provide a further understanding of the syringe and method of the invention. Together with the description, the drawings serve to explain the principles of the invention.